Low cost accumulator device

ABSTRACT

The present invention is directed to an accumulator device and more particularly to an accumulator device having a spherical reservoir chamber which is preferably formed by hydraulic distension of a shell. A casing, bladder, and mounting fixture are combined with the shell by a metal forming operation to thus provide an efficient accumulator with a minimum of forming operations.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is in the field of accumulator devices and isdirected more particularly to a hydraulic accumulator device of the typeused for pulsation dampening and energy storage in hydraulic systems andthe like.

2. The Prior Art

The use of accumulators for energy storage and pulsation dampening istoday common place. A multiplicity of forms of hydraulic accumulatorshave heretofore been employed to satisfy the numerous industrialrequirements therefor.

Typically, a hydraulic accumulator device includes a shell or pressurevessel having an oil port at one end and a gas charging port at theother. The oil port is provided with a nipple fixture or like connectorenabling the same to be connected to the oil line of a hydraulic system.A bladder of elastomeric material is mounted within the pressure vesseland divides the vessel into two discrete chambers namely a chamberconnected with the oil port and a chamber in communication with the gascharging port.

Examples of known fluid pressure accumulators may be found in U.S. Pat.Nos. 3,195,577 of July 20, 1965, 3,211,348 of Oct. 12, 1965 and3,256,911 of June 21, 1966.

While the accumulator devices of the prior art as represented by theabove noted patents provide effective energy storage and dampeningstructures, the costliness of such structures have prevented their widespread use in mass produced environments, such as automobiles, whereinlarge competitive advantages are derived from even small costreductions. More particularly, the pressure vessel components of theprior art devices, which form a principal element of the cost of thedevices and which heretofore have been formed by forging, casting orspinning operations, have mandated a high initial cost factor for theaccumulator. A further cost increasing factor has been the complexity ofthe accumulators of the prior art and the complex methods required fortheir assembly. More particularly, it is frequently necessary to utilizewelding steps both to mount internal components within the accumulatorand to complete the formation of the pressure vessel per se which isoften fabricated of separate halves which must be connected.

SUMMARY OF THE INVENTION

The present invention is directed to a low cost hydraulic accumulatordevice characterized in that the shell or pressure vessel is integrallyformed of a single blank of metal which, after preliminary formingoperations, is hydraulically distended to assume a sphericalconfiguration, at least in the reservoir components thereof. The deviceis further characterized in that the novel mounting assembly enables thebladder, the bladder support and a fixture for connecting theaccumulator to a hydraulic line to be united with the pressure vessel orshell in a single simple forming operation whereby a leakproofconnection is effected. The assembly operation lends itself to massproduction techniques since the novel construction of the componentsautomatically assures that the metal forming operation which integratesthe pressure vessel casing and fixture provides just sufficient pressureon the bladder rim to assure a leakproof connection without damaging thebladder.

More particularly, in accordance with the present invention there isprovided a shell or pressure vessel, the reservoir component of which ispreferably formed by hydraulic distortion of a metal shell or blank tothe desired spherical configuration. The spherical configurationprovides the greatest possible burst resistant strength with a givenmetal thickness and the hydraulic forming operation minimizes thepossibility of the existance of areas of stress concentration within theshell.

The shell includes a neck portion adapted to retain a casing defining asupport for a bladder and a fixture for connection to a hydraulic line.The bladder includes a thickened rim portion which is sandwiched betweenportions of the neck of the shell and portions of a flange extendingfrom the casing. The neck portion is so configured that when the openmouth of the neck portion of the shell is spun or otherwise formed overthe fixture, the rim of the bladder is compressed to an optimum degreeindependent of the spinning force applied, whereby the vessel, thebladder, the casing and the fixture are reliably united into a leakproofunit.

Accordingly, it is an object of the present invention to provide a lowcost hydraulic accumulator device. A further object of the invention isthe provision of a device of the type described wherein the reservoir ofthe pressure shell is spherical in conformation and is formed by ahydraulic distortion process. A further object of the invention is theprovision of a device of the type described which includes a wide mouthbladder portion facilitating fabrication of the bladder, the mouth ofthe bladder providing a retainer rim which is reliably connected to thepressure vessel and remaining components of the accumulator by a simplespinning or like metal deforming operation.

In order more fully to describe the invention and illustrate its usereference is made to the drawing which comprises a vertical sectionalview through the accumulator device in accordance with the invention.

Referring now to the drawing the accumulator device includes a pressurevessel 10 having a generally spherical reservoir portion 11 and a neckportion 12. The other components of the accumulator include a casing 13,a bladder member 14 and an attachment fixture 15.

Optionally, but preferably, the pressure vessel 10 is fabricated byhydraulically outwardly expanding a metal shell or blank afterpreliminary conventional forming operations for shaping the neck, toform the spherical portion 11 by injecting or introducing under extremepressures hydraulic fluids such as oil, water or the like through theneck portion 12 into the interior of the metal shell or blank so as todistend the shell or blank outwardly to cause them to assume theconformation of a surrounding mold or form. The procedures for formingthe shell 10 are detailed in U.S. Pat. No. 2,688,297 of Sept. 7, 1954.Accordingly, further details of the procedure need not be here repeated.

Referring now in greater detail to the configurations of the neckportion 12 of the pressure vessel the same includes an outwardlyradially directed horizontal flange 16 and depending rim portion 17, aradially outwardly directed stop shoulder and a skirt portion 19 whichis initially generally cylindrical in configuration. The casing 13includes a generally cylindrical or partially conical upstanding bladdersupport frame 20 having a rounded upper portion 21. The support portion20 of the casing is provided with a multiplicity of radially directedperforations 22, the casing adjacent its base 23 being provided with aradially directed flange 24.

The bladder member 14, which is widest adjacent its base 25, includes athickened rim portion 26. As will be seen from the inspection of thefigure, the wall thickness of the bladder 14 reduces progressively atdistances further from the base 25 of the bladder, whereby the degree ofstretching upon inflation is greater at portions of the bladder remotefrom the base 25.

The accumulator includes a mounting fixture 15 including a threaded neck27 or like coupling adapted to permit attachment to a hydraulic line.The enlarged base portion 28 of the fixture 15 includes an upwardlyfacing surface portion 29 having formed therein a annular recess 30within which is disposed an O-ring or gasket 31.

The device is assembled by sleeving the bladder 14 over the upstandingportion 20 of the casing 13 and inserting the composite into theinterior of the pressure vessel 10 through the neck portion 12 thereof.Thereafter the fixture 15 is inserted through the open mouth 19 in suchmanner that the upper surface 29 of the fixture engages against thedownwardly directed surface 33 of the flange 24 of the casing 13.

With the parts thus positioned the skirt portion 19 may be deformedinwardly from the dot and dash position of the figure to the solid lineposition 19' of the figure. Such deformation, which may advantageouslybe effected by a spinning operation, forces the upper surface 32 of thefixture tightly against the undersurface 34 of the flange of the casingand at the same time forces the upper surface of the flange against thestop shoulder 18 of the vessel. The noted compressive action in additionto axially compressing the O-ring, tightly clamps the rim portion 26 ofthe bladder 14 between the flange 16 of the pressure vessel and theupper surface of the flange of the casing. It will be recognized thatupward movement of the casing is limited by engagement of the flange ofthe casing against stop shoulder 18. In this manner the degree or extentof compression which may be effected against the rim 26 of the bladder,is controlled and is essentially independent of the force with which theelements 19 bear against the undersurface of the fixture 15.

As is conventional the fixture 15 includes a vertically directed bore 35providing a port or passage for oil to the interior of the accumulator.Prior to use the gas chamber C of the accumulator is charged through gasport 36 which after charging, may be sealed by a valve or by a plugmember 37.

It will thus be perceived that the bladder 14 divides the interior ofthe vessel into two chamber namely the previously described gas chamberC and the chamber C' located within the bladder member 14.

Preferably the accumulator of the instant invention is to be used inconjunction with low volume applications wherein the amount of hydraulicfluid entering the interior of the chamber C' through the oil port 35will be insufficient to expand the bladder beyond about the dotted lineposition thereof 14' whereby the bladder will never engage against theinterior walls of the spherical reservoir portion 11 of the accumulator.

From the foregoing description it will be seen that there is describedin accordance with the present invention an inexpensive and readilyassembled accumulator device particularly suitable for mass productionmanufacture. The hydraulic formation method provides an inexpensivemeans for fabricating a pressure vessel which is stress free and whichis spherical in configuration thereby providing the highest degree ofburst resistance at low cost. The bladder device may be readilyfabricated since the same tapers to a rim portion defining a widestdimension of the bladder whereby bladder molding and removal from themold is simplified. Since the final assembly operation may be effectedby a simple metal turning or spinning operation or the like, assemblycosts are maintained at a minimum. The inherent construction of thedevice assures that the rim portion of the bladder will be compressedonly to a desired degree.

As will be evident to a skilled worker in the art familiarized with theinstant disclosure numerous variations in details of construction may bemade to the disclosed embodiment without departing from the spirit ofthe invention. Accordingly, the invention is to be broadly construedwithin the scope of the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. As a new article ofmanufacture a low cost light weight hydraulic accumulator devicecomprising a unitary metallic shell defining a pressure vessel, saidshell including a spherical reservoir, a generally cylindrical neckportion extending from said reservoir, said neck portion including aradially outwardly extending flange, a rim extending downwardly fromsaid flange in the direction of the axis of said neck portion, a stopshoulder extending radially from said rim portion, a rigid hollowgenerally cylindrical casing extending into said reservoir, said casingincluding throughgoing perforations, a radially directed flange on saidcasing having an upper surface engaging said stop shoulder and a lowersurface, a mounting fixture including an oil port supported in said neckportion, said fixture having a downwardly facing base portion and anupper surface portion engaging said lower surface of said flange of saidcasing, inturned portions of said neck portion underlapping said baseportion of said fixture to clampingly support said fixture and theflange of said casing between said stop shoulder and inturned portions,and a resilient distensable generally cylindrical elastomeric bladdermember disposed over said casing and dividing said reservoir into twochambers, said bladder member having a thickened rim portion defining amouth, said bladder including portions disposed in an annular spacedefined between said neck and said casing, said thickened rim portionbeing clamped in an axially compressed condition between said flange ofsaid neck and said upper surface of said flange of said casing tothereby define a seal between said casing and said vessel at said neckportion.
 2. An accumulator in accordance with claim 1 wherein an annulargasket member is interposed between the upper surface of said fixtureand said lower surface of said flange of said casing, said gasket beingcompressed to define an annular seal area surrounding said oil port bysaid inturned portions.
 3. An accumulator in accordance with claim 2wherein said unitary metallic shell is formed by hydraulically outwardlyexpanding a metallic cup configuration against the configurations of aspherical surrounding cavity.
 4. An accumulator in accordance with claim1 wherein said rim of said bladder member is of a greater diameter thanall portions of said casing but said flange.